Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $91.41   5.793%   $96.7054   $96.71   $96.70   $96.70  
  Purchase #2 $160.29   4.501%   $167.5047   $167.50   $167.50   $167.50  
  Purchase #3 $158.26   9.291%   $172.9639   $172.96   $172.95   $173.00  
  Purchase #4 $222.98   11.180%   $247.9092   $247.91   $247.90   $247.90  
  Purchase #5 $151.40   4.245%   $157.8269   $157.83   $157.85   $157.80  
  Purchase #6 $190.84   9.139%   $208.2809   $208.28   $208.30   $208.30  
  Purchase #7 $80.69   3.396%   $83.4302   $83.43   $83.45   $83.40  
  7 purchase totals = $1,055.87       $1,134.6212   $1,134.62   $1,134.65   $1,134.60